The specific objective of the proposed research is to try to understand how 5-iodo-2'-deoxyuridine (IdUrd) increases alkaline phosphatase activity in the human cancer cell line, HeLa. This effect, originally observed by the applicant, occurs at 5 micron M IdUrd, a concentration which has a relatively small effect on the rate of cell replication. First, the relationship between increased enzyme activity and IdUrd incorporation into DNA will be studied. Antibody made against the purified enzyme will be used to titer the synthesis of alkaline phosphatase molecules in control and IdUrd treated cells to determine if the increased enzymic activity reflects an increase in the synthesis or in the catalytic efficiency of the enzyme. Alkaline phosphatase will also be purified from control and treated cells for kinetic analysis of Km and Vmax as well as examination for a different isozyme pattern. Since cyclic AMP levels as well as phosphorylation of alkaline phosphatase changes when enzyme activity increases in HeLa cells treated with hydrocortisone, cyclic AMP and related enzymes will be investigated after cell growth in IdUrd. If the data indicate that the increased enzymic activity is due to increased enzyme synthesis, then antibody against purified alkaline phosphatase will be employed as outlined in the text to estimate whether IdUrd causes an increase in alkaline phosphatase mRNA.